there are 3 different types of jacksons. xantholophus (generally considered the hardiest of the 3) are widely available, but,
jacksons are a Montane, which makes them a little more sensitive to issues, and not quite as hardy as some of the other cham choices, and because of this, it also makes them less than the ideal choice as a starter chameleon, especially young ones. if you insist on finding this out for yourself, then imo, you should get one at least 6 mths old.
jacksons give live birth, there is no hatching involved. responsible sellers do not usually consider them shippable for at least 2-3 mths. they can be difficult to sex for the first month. you would have better success if you tried to learn about them before you got one, instead of getting one and then trying to learn about it.
imo, you would have a much better chance of success starting off with a veiled. it would be far more rewarding to succeed with a veiled than fail with a jacksons. imo if you really want a to start with a xantholophus, you should do at least several dozen hrs of study first, if you want to have a realistic chance at success. jmo